The present invention relates to improvements in nets, chains or tracks for use on the tires of automotive vehicles. More particularly, the invention relates to improvements in nets, chains or tracks (hereinafter called chains) which can be used on tires consisting of rubber or another elastomeric material, especially on large tires of the type employed on the wheels of heavy-duty earth moving or analogous vehicles.
It is already known to equip the tires of heavy-duty vehicles with chains which enhance the antiskid properties of the wheels and shield the tires from excessive and uneven wear and/or other damage as a result of repeated contact with pieces of rock, gravel, stone or the like. The chains of presently known design normally comprise a network of links each of which has at least one coupling portion extending from the general plane of the respective link and serving to facilitate attachment of the link to a neighboring link. In many instances, the links are or resemble plates having a regular outline and abutting against the external surface of the tire. The aforementioned coupling portions are often disposed in planes which are normal to the planes of the plates of the respective links. Vehicles (normally high-speed vehicles) which employ such chains on their tires include dump trucks, scrapers, levelers (i.e., vehicles which are used for smoothing horizontal or sloping terrain), front loaders as well as a wide variety of additional earth moving or analogous heavy-duty vehicles which are designed to travel at speeds of up to and even in excess of 40 mph. The tires on the wheels of such vehicles are often huge and highly expensive so that the provision of chains which shield the tires and prolong their useful life is not only desirable and warranted but also necessary in the interest of economy.
Canadian Pat. No. 182,055 discloses a chain which is to be used on the tires of the aforediscussed types of vehicles and includes substantially plate-like links which abut against the external surface of the tire and are coupled to each other. The coupling means include integral portions of the links which extend outwardly from the general planes of the respective plates. The planes of such integral coupling portions are normally disposed at an angle of approximately 90.degree. to the planes of the corresponding plates. The means for coupling the plates of neighboring links to each other further comprises annular coupling elements which resemble the elements of a conventional rudimentary chain and serve to join the coupling portions of neighboring links, preferably in such a way that the sides of neighboring links are parallel to each other. The annular coupling elements are parallel to each other and extend substantially at right angles to the sides of the links. The assembly can be completed without resort to a welding operation. This is highly desirable because the absence of welding operations reduces the initial cost of the chain. The reduction in cost is surprisingly pronounced in view of the ever-increasing cost of welding.
The patented chain exhibits a number of serious drawbacks. Thus, such chain must be assembled of a relatively large number of different components which contributes to the initial cost of the ultimate product. This is due to the fact that the aforementioned annular coupling elements must be secured to pin-shaped coupling portions by suitable locking devices including rings which are fastened to the links. The assembly of plate-like links with pin-shaped coupling portions, annular coupling elements and means for locking the coupling elements to the respective pin-shaped coupling portions is subject to very pronounced wear and to pronounced stresses, e.g., during travel of the vehicle on rocky terrain where the parts of the chains strike against sharp pieces of rock, gravel or the like. Therefore, the useful life of such chains is relatively short as a result of extensive wear and/or breakage of their components.
It is further known to assemble a chain for use on the tires of wheels of heavy-duty vehicles by resort to welded components. German Utility Model No. 18 80 605 discloses an antiskid chain which is assembled of flat and oval vertical components and ring-shaped welded horizontal components. The welding operation cannot be avoided in view of the specific design of the just mentioned components. In addition to the drawbacks resulting from the need for welding (namely, high initial cost, secondary heat-treatment after welding, and others), the longitudinal cross-sectional area of the vertical components of such chains is relatively small and each such component has a relatively small surface which contacts the ground and is thus subject to wear when the vehicle is in use. This reduces the useful life of the chain because a relatively small amount of wear upon the vertical components renders the chain useless for its intended purpose. An inversion of such chains (inside out) is not possible because the vertical components undergo one-sided wear as a result of repeated tilting which cannot be avoided in view of unstable mounting of such vertical components. In other words, the vertical components are coupled to the horizontal components in such a way that their tilting in response to engagement with the ground is unavoidable with attendant unpredictable (one-sided) wear which prevents the further use of such chains in inverted position.
German Auslegeschrift No. 18 17 170 discloses a chain which employs relatively narrow stilt-like vertical components having small tire-contacting surfaces so that the mounting of these vertical components inveriably entails at least some tilting. The chain which is disclosed in this German publication need not employ any welded components in that endless band-like portion thereof which surrounds the tread of the tire; however, the components which connect the band-like portion to the lateral chains for the tire invariably include welded parts. Moreover, and as already mentioned above, the stilt-like vertical components of the band-like portion of the chain are unstable, i.e., the horizontal components cannot prevent tilting of vertical components with the result that the vertical components are subjected to unpredictable and normally one-side wear. Still further, tilting of the vertical components promotes wear so that the useful life of such chains is very short and the chains cannot be used in inverted position. Each and every revolution of the wheel entails pronounced tilting of the vertical components. The pronouncedness of such tilting movements is attributable not only to the configuration and manner of mounting of the vertical components but also to the fact that the horizontal components of the chain are unstable, i.e., the horizontal components cannot offer sufficient resistance to tilting of the vertical components. It has been found that the uneven and unpredictable wear upon the vertical components is so pronounced that a chain of such construction must be discarded well ahead of the time when the same chain would require replacement were the wear upon the vertical components uniform, i.e., if the wear would be ideal so that the entire portion of each vertical component which is provided for the express purpose of wearing away would be used up prior to the need for replacement of the chain. As a rule, one-sided wear upon the vertical components of the chain results in the formation of sharp edges which prevent an inversion of the chain after a certain period of use.
Still another drawback of the just discussed conventional chain is that its dimensions increase (not only in the circumferential direction but also transversely of the tread of the tire) with progressing wear. This necessitates frequent tensioning of the chain. However, the extent to which the chain can be tensioned is rather limited and, furthermore, repeated tensioning results in a shift of the endless band-like portion of the chain with reference to the tread (i.e., with reference to the ideal position of the band-like portion relative to the tire) so that the inclination of the vertical components increases from a relatively small acute angle toward a position in which the vertical components are disposed at or close to a right angle with reference to the direction of travel. This, too, contributes to more pronounced stressing of, and hence to a more pronounced wear upon, the vertical components. Moreover, the chain which is disclosed in the aforementioned German Auslegeschrift exhibits the drawback that it must employ a large number of locking bolts along both marginal portions of the endless band-like part of the chain.
A drawback which is common to all heretofore known chains is that the lateral chains which shield the inner and outer sides of the tires must include welded components whose shielding or protecting action is unsatisfactory and whose cost is extremely high.